Switched capacitor circuits are known. Such circuits are the product of circuit design techniques commonly used to miniaturize (integrate) components. In portable (hand-held) communication applications, components such as filters are often reduced to integrated circuit (IC) form. A switched capacitor circuit utilizes the fact that when a capacitor is switched between a signal to be sampled and ground at a rate many times that of the frequency of the sampled signal, the capacitor will simulate the circuit behavior of a resistor.
To save the current drain (energy consumption) of a switched capacitor circuit, it is known to activate the switched capacitor circuit only when it is needed and to fully deactivate it when it is not in use. This provides maximized energy savings since the circuit only draws current when activated. However, substantial DC transient currents are produced when the switched capacitor circuit is turned ON and OFF (i.e., activated and deactivated). These DC transients increase the settling time required before information can be passed through the circuits, and therefore, cannot be used in a system that requires fast turn-on time.
Another problem exists for the conventional battery saving technique of turning the switched capacitor circuit ON and OFF. For those communication applications that require continuous operation, such as squelch, discontinuities in the applied power would interrupt such operations, and therefore, would not be usable. Hence, a need exists to lower the current drain of switched capacitor circuits without introducing transient switching currents.